A roller bearing has a large load capacity of a radial load compared to a ball bearing, and a tapered roller bearing in which a roller having a circular truncated cone shape (a tapered roller) is assembled as a rolling element can support a combined load of a radial load and an axial (thrust) load. For this reason, the tapered roller bearing has been widely used for a rotating support portion in a driving device, a gear reducer, and a power transmitting device in various machines such as a motor vehicle, a railway vehicle, a construction machine, a machine tool, and an industrial robot (for example, refer to Patent Document 1).
As a cage used in the tapered roller bearing, a resin cage which is made by injection-molding a thermoplastics resin with which a reinforcing material such as a glass fiber or a carbon fiber is filled has been widely used since the resin cage is excellent in lightness and mass productivity and has no metallic abrasion powders generated compared with a metal cage which is made by press-forming a steel plate. In addition, in order to reduce manufacturing cost, the resin cage is generally injection-molded by using a molding structure in which a pair of molds are separated from each other in the axial direction, that is, by using an axial-draw molding (for example, refer to paragraph [0011] and FIG. 11 in Patent Document 1).
In the cage which is injection-molded by using such an axial-draw molding, on the basis of a mold parting line in a pocket as a boundary, one side is in contact with the tapered roller and the other side is not in contact with the tapered roller. Thus, the tapered roller can be inserted into the cage from the inner diameter side, and is not dropped out to the outer diameter side, but is dropped out to the inner diameter side. Therefore, since the tapered roller is likely to be dropped out with only the cage and the tapered roller, the productivity of the tapered roller bearing deteriorated depending on a configuration of an assembly line.
In addition, in order to improve the productivity of the tapered roller bearing, there has been proposed a resin cage for a tapered roller bearing which has a shape realizing a so-called cage and roller wherein the cage can support the tapered roller while holding the tapered roller in a state where the tapered roller bearing is not assembled between the inner ring and the outer ring (for example, refer to Patent Documents 2 and 3).